they are allowed on, but only when invited. this ensures, that when i have people over the dogs dont jump on the sofa with them. not everyone is comfortable with it. they are allowed to "ask" to come up though. when it is appropriate i allow them on. when not i tell them to go to their bed. most of the time, they know that when i am alone, they are allowed on.
i'm currently sleeping on a couch bed in my living room. and they know at night, they are allowed on without invitation. they often get up during the night to have some water, or lie on the floor if they are too warm, and then come back up. it's ok with me, as long as they dont step on me. if i dont want them sleeping with me, then i sleep in my bedroom...